use core::convert::TryInto;
// use cortex_m_semihosting::hprintln;

use crate::{
    peripherals::flash::Flash,
    typestates::init_state::Enabled,
    traits::flash::{
        Error,
        Result,
        Read,
        WriteErase,
    },
};

pub use generic_array::{
    GenericArray,
    typenum::{U16, U512},
};

// one physical word of Flash consists of 128 bits (or 4 u32, or 16 bytes)
// one page is 32 physical words, or 128 u32s, or 512 bytes)

// reads must be physical word aligned (16 bytes)
// erase and write must be page aligned (512 bytes)

pub const READ_SIZE: usize = 16;
pub const WRITE_SIZE: usize = 512;
pub const PAGE_SIZE: usize = 512;

pub struct FlashGordon {
    flash: Flash<Enabled>,
}

impl FlashGordon {
    pub fn new(flash: Flash<Enabled>) -> Self {

        flash.raw.event.write(|w| w.rst().set_bit());
        // seems immediate
        while flash.raw.int_status.read().done().bit_is_clear() {}

        // first thing to check! illegal command
        debug_assert!(flash.raw.int_status.read().err().bit_is_clear());
        // first thing to check! legal command failed
        debug_assert!(flash.raw.int_status.read().fail().bit_is_clear());

        FlashGordon {
            flash,
        }
    }

    fn clear_status(&self) {
        self.flash.raw.int_clr_status.write(|w| w
            .done().set_bit()
            .ecc_err().set_bit()
            .err().set_bit()
            .fail().set_bit()
        );

    }

    fn status(&self) -> Result {
        let status = self.flash.raw.int_status.read();
        // if status.done().bit_is_clear() {
        //     return Err(Error::Busy);
        // }
        if status.err().bit_is_set() {
            return Err(Error::Illegal);
        }
        if status.ecc_err().bit_is_set() {
            return Err(Error::EccError);
        }
        if status.fail().bit_is_set() {
            return Err(Error::Failure);
        }

        Ok(())
    }

    pub fn just_program_at(
        &mut self,
        address: usize,
    ) -> Result {

        let flash = &self.flash.raw;
        assert!(flash.int_status.read().done().bit_is_set());
        self.clear_status();

        flash.event.write(|w| w.rst().set_bit());
        // seems immediate
        while flash.int_status.read().done().bit_is_clear() {}
        self.status()?;
        self.clear_status();

        flash.starta.write(|w| unsafe { w.starta().bits((address >> 4) as u32) } );
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Program as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        debug_assert!(flash.int_status.read().err().bit_is_clear());
        debug_assert!(flash.int_status.read().fail().bit_is_clear());
        self.status()?;

        Ok(())

    }

    pub fn clear_page_register(&mut self) {
        let flash = &self.flash.raw;
        assert!(flash.int_status.read().done().bit_is_set());
        self.clear_status();

        for i in 0..32 {
            for j in 0..4 {
                flash.dataw[j].write(|w| unsafe { w.bits(0x0) });
            }
            flash.starta.write(|w| unsafe { w.starta().bits(i as u32) } );
            flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Write as u32) });

            while flash.int_status.read().done().bit_is_clear() {}
            debug_assert!(flash.int_status.read().err().bit_is_clear());
            debug_assert!(flash.int_status.read().fail().bit_is_clear());
            assert!(self.status().is_ok());
        }
    }

    pub fn write_u8(&mut self, address: usize, byte: u8) -> Result {
        self.clear_page_register();
        let flash = &self.flash.raw;
        // which "physical word" is this?
        let page_register_column = (address & (512 - 1)) >> 4;
        let mut word = [0u8; 4];
        word[address % 4] = byte;
        // redundant since done in clear_page_register
        for j in 0..4 {
            flash.dataw[j].write(|w| unsafe { w.bits(0) });
        }
        flash.dataw[(address >> 2) % 4].write(|w| unsafe { w.bits(u32::from_ne_bytes(word)) });
        flash.starta.write(|w| unsafe { w.starta().bits(page_register_column as u32) } );
        self.clear_status();
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Write as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        self.status()?;

        self.clear_status();
        // self.just_program_at(address & !(512 - 1));
        flash.starta.write(|w| unsafe { w.starta().bits((address >> 4) as u32) } );
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Program as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        self.status()?;
        Ok(())
    }

    pub fn write_u32(&mut self, address: usize, word: u32) -> Result {
        self.clear_page_register();
        let flash = &self.flash.raw;

        // which "physical word" is this?
        let page_register_column = (address & (512 - 1)) >> 4;
        // redundant since done in clear_page_register
        for j in 0..4 {
            flash.dataw[j].write(|w| unsafe { w.bits(0) });
        }
        flash.dataw[(address >> 2) % 4].write(|w| unsafe { w.bits(word) });
        flash.starta.write(|w| unsafe { w.starta().bits(page_register_column as u32) } );
        self.clear_status();
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Write as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        self.status()?;

        self.clear_status();
        // self.just_program_at(address & !(512 - 1));
        flash.starta.write(|w| unsafe { w.starta().bits((address >> 4) as u32) } );
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Program as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        self.status()?;

        Ok(())
    }

    pub fn write_u128(&mut self, address: usize, data: u128) -> Result {
        // self.clear_page_register();

        let flash = &self.flash.raw;

        let buf: [u8; 16] = data.to_ne_bytes();

        for (i, chunk) in buf.chunks(4).enumerate() {
            flash.dataw[i].write(|w| unsafe { w.bits(u32::from_ne_bytes(chunk.try_into().unwrap())) } );
        }
        flash.starta.write(|w| unsafe { w.starta().bits((address >> 4) as u32) } );
        self.clear_status();
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Write as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        self.status()?;

        self.clear_status();
        // self.just_program_at(address & !(512 - 1));
        flash.starta.write(|w| unsafe { w.starta().bits((address >> 4) as u32) } );
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Program as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        self.status()?;

        Ok(())
    }

    pub fn read_u128(&mut self, address: usize) -> u128 {
        let mut buf = [0u8; 16];
        self.read(address, &mut buf);
        u128::from_ne_bytes(buf)
    }
}

impl Read<U16> for FlashGordon {
    // this reads 16B or one flash word
    // address is in bytes, whereas starta expects address in flash words
    // so starta = address / 16 = address >> 4
    fn read_native(&self, address: usize, array: &mut GenericArray<u8, U16>) {
        // hprintln!("native read from {} of {:?} (first 16)", address, &array[..16]).ok();
        let flash = &self.flash.raw;

        assert!(flash.int_status.read().done().bit_is_set());
        self.clear_status();
        // if self.status().is_err() {
        //     cortex_m_semihosting::dbg!(flash.int_status.read().bits());
        //     assert!(self.status().is_ok());
        // }
        assert!(self.status().is_ok());

        let addr = address as u32;
        debug_assert!(addr & (READ_SIZE as u32 - 1) == 0);

        flash.starta.write(|w| unsafe { w.starta().bits(addr >> 4) } );
        // want to have normal reads
        flash.dataw[0].write(|w| unsafe { w.bits(0) } );
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::ReadSingleWord as u32) });
        while flash.int_status.read().done().bit_is_clear() { continue; }

        assert!(flash.int_status.read().err().bit_is_clear());
        debug_assert!(flash.int_status.read().fail().bit_is_clear());

        // each dataw[i] now contains 4 bytes
        for (i, chunk) in array.chunks_mut(4).enumerate() {
            chunk.copy_from_slice(&flash.dataw[i].read().bits().to_ne_bytes());
        }
    }
}

impl WriteErase<U512, U512> for FlashGordon {

    fn status(&self) -> Result {
        self.status()
    }

    // TODO: use critical section?
    fn erase_page(&mut self, page: usize) -> Result {
        // starta is still in flash words, of which a page has 32
        let starta = page * 32;
        // hprintln!("native erase page {}", page).ok();

        let flash = &self.flash.raw;
        assert!(flash.int_status.read().done().bit_is_set());
        self.clear_status();
        assert!(flash.int_status.read().done().bit_is_clear());

        flash.starta.write(|w| unsafe { w.starta().bits(starta as u32) } );
        flash.stopa.write(|w| unsafe { w.stopa().bits(starta as u32) } );
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::EraseRange as u32) });
        while flash.int_status.read().done().bit_is_clear() {}

        debug_assert!(flash.int_status.read().err().bit_is_clear());
        debug_assert!(flash.int_status.read().fail().bit_is_clear());
        // cortex_m_semihosting::dbg!(self.status());
        self.status()?;

        Ok(())
    }

    fn write_native(
        &mut self,
        address: usize,
        array: &GenericArray<u8, U512>,
        // cs: &CriticalSection,
    ) -> Result {

        // hprintln!("native write to {} of {:?} (first 16)", address, &array[..16]).ok();
        let flash = &self.flash.raw;
        assert!(flash.int_status.read().done().bit_is_set());
        self.clear_status();

        // maybe check the page is erased?

        // write one physical word (16 bytes) at a time
        for (i, chunk) in array.chunks(16).enumerate() {
            let starta = (address >> 4) + i;
            flash.starta.write(|w| unsafe { w.starta().bits(starta as u32) } );

            for (j, word) in chunk.chunks(4).enumerate() {
                flash.dataw[j].write(|w| unsafe { w.bits(
                    u32::from_ne_bytes(word.try_into().unwrap())
                ) } );
            }

            flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Write as u32) });
            // flash.cmd.write(|w| unsafe { w.bits(FlashCommands::WriteProgram as u32) });
            while flash.int_status.read().done().bit_is_clear() {}
            debug_assert!(flash.int_status.read().err().bit_is_clear());
            debug_assert!(flash.int_status.read().fail().bit_is_clear());
            self.status()?;
        }
        self.clear_status();

        let starta = address >> 4;
        flash.starta.write(|w| unsafe { w.starta().bits(starta as u32) } );
        flash.cmd.write(|w| unsafe { w.bits(FlashCommands::Program as u32) });
        while flash.int_status.read().done().bit_is_clear() {}
        debug_assert!(flash.int_status.read().err().bit_is_clear());
        debug_assert!(flash.int_status.read().fail().bit_is_clear());
        self.status()?;

        Ok(())

    }
}

#[allow(dead_code)]
#[repr(C)]
pub enum FlashCommands {
    Init = 0x0,
    PowerDown = 0x1,
    SetReadMode = 0x2,
    ReadSingleWord = 0x3,
    EraseRange = 0x4,
    BlankCheck = 0x5,
    MarginCheck = 0x6,
    Checksum = 0x7,
    Write = 0x8,
    WriteProgram = 0xA,
    Program = 0xC,
    /// report ECC error (correction) count
    ReportEcc= 0xD,
}

#[cfg(feature = "littlefs")]
#[allow(non_camel_case_types)]
pub mod littlefs_params {
    use super::*;
    pub const READ_SIZE: usize = 16;
    pub const WRITE_SIZE: usize = 512;
    pub const BLOCK_SIZE: usize = 512;

    // no wear-leveling for now
    pub const BLOCK_CYCLES: isize = -1;

    pub type CACHE_SIZE = U512;
    pub type LOOKAHEADWORDS_SIZE = U16;
}

#[cfg(feature = "littlefs")]
#[macro_export]
macro_rules! littlefs2_filesystem {
    ($Name:ident: (
        $BASE_OFFSET:expr
    )) => {
        littlefs2_filesystem!(
            $Name: (
                $BASE_OFFSET,
                //     631.5KB
                ((631 * 1024 + 512) - $BASE_OFFSET) / 512
            )
        );
    };
    ($Name:ident: (
        $BASE_OFFSET:expr,
        $BLOCK_COUNT:expr
    )) => {
        //
        // Compile time assertion that $BASE_OFFSET is 512 byte aligned.
        const _ZERO_SIZED_CHECK: usize = ((core::mem::size_of::<[u8; ($BASE_OFFSET % 512)]>() == 0) as usize) - 1;
        // Compile time assertion that flash region does NOT spill over the 631.5KB boundary.
        const _OVERFLOW_SIZE_CHECK: usize = ((
            core::mem::size_of::<[u8; (($BASE_OFFSET + $BLOCK_COUNT * 512) <= (631 * 1024 + 512)) as usize]>() == 1) as usize) - 1;

        pub struct $Name {
            flash_gordon: $crate::drivers::flash::FlashGordon
        }

        impl $Name {
            const BASE_OFFSET: usize = $BASE_OFFSET;

            pub fn new (flash_gordon: $crate::drivers::flash::FlashGordon) -> Self {
                Self { flash_gordon }
            }
        }

        impl littlefs2::driver::Storage for $Name {
            const READ_SIZE: usize = $crate::drivers::flash::littlefs_params::READ_SIZE;
            const WRITE_SIZE: usize = $crate::drivers::flash::littlefs_params::WRITE_SIZE;
            const BLOCK_SIZE: usize = $crate::drivers::flash::littlefs_params::BLOCK_SIZE;

            const BLOCK_COUNT: usize = $BLOCK_COUNT;
            const BLOCK_CYCLES: isize = $crate::drivers::flash::littlefs_params::BLOCK_CYCLES;

            type CACHE_SIZE = $crate::drivers::flash::littlefs_params::CACHE_SIZE;
            type LOOKAHEADWORDS_SIZE = $crate::drivers::flash::littlefs_params::LOOKAHEADWORDS_SIZE;


            fn read(&self, off: usize, buf: &mut [u8]) -> LfsResult<usize> {
                <$crate::drivers::flash::FlashGordon as $crate::traits::flash::Read<$crate::drivers::flash::U16>>
                    ::read(&self.flash_gordon, Self::BASE_OFFSET + off, buf);
                Ok(buf.len())
            }

            fn write(&mut self, off: usize, data: &[u8]) -> LfsResult<usize> {
                let ret = <$crate::drivers::flash::FlashGordon as $crate::traits::flash::WriteErase<$crate::drivers::flash::U512, $crate::drivers::flash::U512>>
                    ::write(&mut self.flash_gordon, Self::BASE_OFFSET + off, data);
                ret
                    .map(|_| data.len())
                    .map_err(|_| littlefs2::io::Error::Io)
            }

            fn erase(&mut self, off: usize, len: usize) -> LfsResult<usize> {
                let first_page = (Self::BASE_OFFSET + off) / 512;
                let pages = len / 512;
                for i in 0..pages {
                    <$crate::drivers::flash::FlashGordon as $crate::traits::flash::WriteErase<$crate::drivers::flash::U512, $crate::drivers::flash::U512>>
                        ::erase_page(&mut self.flash_gordon, first_page + i)
                        .map_err(|_| littlefs2::io::Error::Io)?;
                }
                Ok(512 * len)
            }

        }
    //
    }
}

#[cfg(feature = "littlefs")]
#[macro_export]
macro_rules! littlefs2_prince_filesystem {
    ($Name:ident: (
        $BASE_OFFSET:expr
    )) => {
        littlefs2_prince_filesystem!(
            $Name: (
                $BASE_OFFSET,
                //     631.5KB
                ((631 * 1024 + 512) - $BASE_OFFSET) / 512
            )
        );
    };
    ($Name:ident: (
        $BASE_OFFSET:expr,
        $BLOCK_COUNT:expr
    )) => {
        //
        // Compile time assertion that $BASE_OFFSET is 512 byte aligned.
        const _ZERO_SIZED_CHECK_0: usize = ((core::mem::size_of::<[u8; ($BASE_OFFSET % 512)]>() == 0) as usize) - 1;
        // Compile time assertion that flash region does NOT spill over the 631.5KB boundary.
        const _OVERFLOW_SIZE_CHECK_0: usize = ((
            core::mem::size_of::<[u8; (($BASE_OFFSET + $BLOCK_COUNT * 512) <= (631 * 1024 + 512)) as usize]>() == 1) as usize) - 1;


        pub struct $Name {
            flash_gordon: $crate::drivers::flash::FlashGordon,
            prince: $crate::peripherals::prince::Prince<$crate::typestates::init_state::Enabled>,
        }

        impl $Name {
            const BASE_OFFSET: usize = $BASE_OFFSET;

            pub fn new (
                flash_gordon: $crate::drivers::flash::FlashGordon,
                prince: $crate::peripherals::prince::Prince<$crate::typestates::init_state::Enabled>,
            ) -> Self {
                Self { flash_gordon, prince }
            }
        }

        impl littlefs2::driver::Storage for $Name {
            const READ_SIZE: usize = $crate::drivers::flash::littlefs_params::READ_SIZE;
            const WRITE_SIZE: usize = $crate::drivers::flash::littlefs_params::WRITE_SIZE;
            const BLOCK_SIZE: usize = $crate::drivers::flash::littlefs_params::BLOCK_SIZE;

            const BLOCK_COUNT: usize = $BLOCK_COUNT;
            const BLOCK_CYCLES: isize = $crate::drivers::flash::littlefs_params::BLOCK_CYCLES;

            type CACHE_SIZE = $crate::drivers::flash::littlefs_params::CACHE_SIZE;
            type LOOKAHEADWORDS_SIZE = $crate::drivers::flash::littlefs_params::LOOKAHEADWORDS_SIZE;


            fn read(&self, off: usize, buf: &mut [u8]) -> LfsResult<usize> {
                self.prince.enable_region_2_for(||{
                    let flash: *const u8 = (Self::BASE_OFFSET + off) as *const u8;
                    for i in 0 .. buf.len() {
                        buf[i] = unsafe{ *flash.offset(i as isize) };
                    }
                });
                Ok(buf.len())
            }

            fn write(&mut self, off: usize, data: &[u8]) -> LfsResult<usize> {
                let prince = &mut self.prince;
                let flash_gordon = &mut self.flash_gordon;
                let ret = prince.write_encrypted(|prince| {
                    prince.enable_region_2_for(||{
                        <$crate::drivers::flash::FlashGordon as
                            $crate::traits::flash::WriteErase<$crate::drivers::flash::U512, $crate::drivers::flash::U512>>
                            ::write(flash_gordon, Self::BASE_OFFSET + off, data)
                    })
                });
                ret
                    .map(|_| data.len())
                    .map_err(|_| littlefs2::io::Error::Io)
            }

            fn erase(&mut self, off: usize, len: usize) -> LfsResult<usize> {
                let first_page = (Self::BASE_OFFSET + off) / 512;
                let pages = len / 512;
                for i in 0..pages {
                    <$crate::drivers::flash::FlashGordon as
                        $crate::traits::flash::WriteErase<$crate::drivers::flash::U512, $crate::drivers::flash::U512>>
                        ::erase_page(&mut self.flash_gordon, first_page + i)
                        .map_err(|_| littlefs2::io::Error::Io)?;
                }
                Ok(512 * len)
            }

        }
    //
    }
}

// Example implementations using 0x8_0000 boundary to separate code and data.
// This leaves 128KB for data and is covered by the last prince region (region 2).
// ```
// littlefs2_filesystem!(FilesystemGordon: (0x8_0000));
// ```